#!/bin/bash
#
# askpass_stars [prompt]
#
# TTY password reading with stars echoed instead of user keys.
#
# Handles backspaces, deletes, newlines and returns in a manner consistant for
# password reading. Also handles a kill-line (^U) input, while TABs and other
# control characters are ignored.
#
# The latest version can be downloaded from
#     https://antofthy.gitlab.io/software/#askpass_stars
#
###
#
# BUG: Interupts are handled simply, basically to restore TTY settings.
# Idealy it should flag the interupt, and kill the bash "read" so as
# to break the input reading loop.
#
####
#
# Anthony Thyssen, 30 June 2017
#
unset PWORD
PWORD=

# -----------------------------------------------------------
# If no TTY just read one line from stdin, and output it (short circuit)
if ! tty >/dev/null;  then
  read -r -s PWORD
  echo "$PWORD"
  exit 0
fi

# Ensure Solaris UNIX machines use the UCB "stty" command
PATH="/usr/bin:/bin"
export PATH

# -----------------------------------------------------------
# Use the systemd ask password program (if available)

# If a binary version is available -- use it!
if [ "X$1" = "X-f" ]; then
  # force the use of this shell script version
  shift
elif [ -x /bin/systemd-ask-password ];  then
  # use the systemd version - without a timeout
  # Warning "sudo" with interupt - can leave the TTY in a bad state!
  # Thus I save and restore the TTY settings
  stty_save=`stty -g`
  trap 'stty "$stty_save"' EXIT
  /bin/systemd-ask-password --timeout=0 "${1:-Password: }"
  exit $?
fi

# -----------------------------------------------------------
# My version of user password requests

# Get prompt
prompt="${*:-Password:}" # any other argument is the prompt to use

star='#'  # Yes I know it is not a star!
          # But I wanted it to be different to systemd-ask-password

# Grab the current TTY settings
# Save stdout (for password result) to descriptor 3
# Otherwise read and write to the users TTY
# Gnu and Linux "stty" uses stdin for the terminal to adjust
# BUT:  Solaris /usr/ucb/stty command uses stdout and NOT stdin!
exec 3>&1 </dev/tty >/dev/tty
stty_save=`stty -g`
trap 'stty "$stty_save"' EXIT
trap 'echo "===INTERUPT==="; exit 10' HUP INT QUIT ABRT TERM

# Turn off echo and control character handling...
# This stops BASH constantaly switching terminal modes when reading each
# character, and allow a fast typing user still have characters echoed between
# reads.
#
stty -icanon -echo
#stty -echo           # turn off echo - but not controls!

# Prompt and read password one character at a time
echo -n "$prompt "
while IFS= read -r -n1 char; do
  # Convert users key press to hexadecimal character code
  # Note a 'return' or EOL, will return a empty string
  #code=$( echo -n "$char" | od -An -tx1 | tr -d ' \011' )
  code=${char:+$(printf '%02x' "'$char'")} # if value convert
  #echo -n "'$code'"  # DEBUGGING

  case "$code" in
  ''|0a|0d) break ;;               # Finish on EOF, Null, LineFeed, or Return
  03) error_exit=true; break ;;    # ^C Interrupt
  08|7f)                           # Backspace or Delete
      if [ -n "$PWORD" ]; then
        PWORD="$( echo "$PWORD" | sed 's/.$//' )"
        echo -n $'\b \b'           # not available on older shells
      fi
      ;;
  15)                              # ^U or kill line
      echo -n "$PWORD" | tr -c '\010' '\010'  # backspace
      echo -n "$PWORD" | tr -c ' '    ' '     # clear stars
      echo -n "$PWORD" | tr -c '\010' '\010'  # backspace
      #echo -n "$PWORD" | sed 's/./\cH \cH/g' # using gnu-sed
      PWORD=''
      ;;
  [01]?) ;;                        # Ignore ALL other control characters
  *)  PWORD="$PWORD$char"          # Normal char - record it
      echo -n "$star"
      ;;
  esac
done

# Return TTY to normal, cancel exit trap
stty "$stty_save"
trap - EXIT HUP INT QUIT TERM

# Remove all the stars now that the input is finished (same as '15' above)
#echo -n "$PWORD" | tr -c '\010' '\010'  # backspace
#echo -n "$PWORD" | tr -c ' '    ' '     # clear stars
#echo -n "$PWORD" | tr -c '\010' '\010'  # backspace
#echo -n "$PWORD" | sed 's/./\cH \cH/g'

echo ""  # "===password accepted===" ;;

# Output the resulting password to the original stdout
echo "$PWORD" >&3

exit 0